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| DTV questions http://interceptradio.com/bbs/viewtopic.php?f=8&t=3266 |
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| Author: | DennisE [ Fri Oct 23, 2009 8:48 am ] |
| Post subject: | DTV questions |
I'm using tvfool.com to get a 'radar' plot of stations that can be monitored from Monroe area and the other resources I'm using to research are a spectrum analyzer and the FCC web site has the form of http://www.fcc.gov/fcc-bin/tvq?call=???? (just enter TV station call letters) to get license data. -- Observations. Altho licensed for broadcasting on various UHF channels Ch 9, 11 and 13 are broadcasting DTV on their legacy VHF freqs. But the spectrum analyzer display 9 and 11 look nothing like the DTV signals for the rest of the stations in the area. I also use http://www.tscm.com/TSCM101HDTV.html as a reference. TSCM is a great site for bugging issues. We have the DigitalStream converter. The modulation scheme is clearly different for 9 & 11 but what is it called? Altho the FCC granted 9, 11 and 13 UHF channels, they still use the VHF. So what's that all about? -- I assume the TV stations were using omni antennas and I started in on this investigation trying to figure out what KING, broadcasting on UHF channel 48 had a weaker signal. About 8-12 dBM lower. The difference is notable when we have rain cells between the shack here on a hill north of Monroe and Seattle. Then I looked at the polar plots and did some calculations. This Digital Stream converter gives a relative signal strength reading (0-100). The relative difference between KING's signal and KOMO or KIRO as reported by the DTV converter matched the polar plot signal strengths really well. Oh, tscm.com/TSCM101video3.html has a pretty neat 'tutorial' on surveillance video. |
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| Author: | DennisE [ Fri Oct 23, 2009 9:02 am ] |
| Post subject: | Re: DTV questions |
The other issue that seems odd is I'm picking up with the spec analyzer the 764-meg KSTW Ch 11 translator on Blyn Mtn, but the signal doesn't have video, just FM audio. I used the database on this site to see what it might be. |
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| Author: | Rich [ Fri Oct 23, 2009 9:37 am ] |
| Post subject: | Re: DTV questions |
Most stations run their DTV on UHF with the option of moving them back to VHF once analog is totally gone. Perhaps some of these stations are still running the loop tape "how to hook up your DTV converter box" on their VHF ? What does the spectrum look like ? Analog TV should have a wide VSB AM signal plus an FM audio carrier. DTV should always look the same (6mhz wide with very sharp dropoffs). The data goes through a randomizer so the signal should have a constant look on the RF side. |
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| Author: | Kerwin [ Mon Oct 26, 2009 6:56 pm ] |
| Post subject: | Re: DTV questions |
Stations had an option to "elect" to use their "temporary" UHF DTV channel as their permanant post-transition channel. Some local stations such as KOMO and KING had low VHF channels that were outside of the "core" channels and elected to remain on UHF. KCTS; KSTW; and KCPQ in the upper VHF elected to establish post-transition DTV on their VHF channels and terminate DTV on their temporary UHF channels. Originally it was thought that upper VHF would work just fine at lower power levels with DTV but that seems to not be the case. KCTS is stuck at 27 KW and due to Canadian issues can't increase power. KSTW recently increased to 100 KW, and KCPQ may add a translator on the old KMYQ ch 22 for better coverage in Seattle and eastern King County. As an iterim measure they are simulcasting the ch 13.1 HD signal as SD on ch 22.2. Lots of Seattle area DTV issues are discussed at: http://www.avsforum.com/avs-vb/showthre ... 4&t=254620 Kerwin |
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